Control arrangement for fluid operated circuit breakers



Mud! 1950 J. w. IMMERMAN JR. ETAL 2,500,777

comer. mmcmmu'l FOR FLUID. OPERATED cmcurr BREAKERS Filed April 20, 1945' 2 Sheets-Sheet 1 Fi gl.

' Insulatiofi Inventor-s: Julius TmmermamJrz,

P E Bol 1 NWL,

T h en'- Abt car-neg.

2 sheqts sheet 2 AL comm. mmcmm FOR um OPERATED CIRCUIT BREAKERS J. W. TIMMERMAN March 14, 1950 Filed April 20, 1945 a 9 e H mm J om MW mt J A m h f. r W WW and difllcult to manufacture.

Patented Mar. 14, 1950 UNITED STATES PATENT OFFICE CONTROL ARRANGEMENT FOR FLUID OPERATED CIRCUIT BREAKERS New York Application April 20, 1945, Serial No. 589,288

16 Claims. 1

Our invention relates to a control arrangement for electric, circuit breakers, and more specifically to a control arrangement for fluid operated circuit breakers.

Fluid operated circuit breakers since the advent of the gas blast circuit breaker, have become very popular and are today extensively used. Heretofore control systems for fluid operated circuit breakers have been very complicated and as a consequence thereof they are expensive It would be desirable to provide a control arrangement for a fluid operated circuit breaker which enables one to effect all the desired controls of the circuit breaker and yet wherein the control arrangement is simple, dependable and positive in effecting the desired regulation.

Accordingly it is an object of our invention to provide a new and improved control arrangement for electric circuit breakers of the fluid operated type which is considerably less complicated than arrangements used heretofore.

It is another object of our invention to provide a simple control arrangement for fluid .operated electric circuit breakers which provides the desired relationship with respect to opening and closing of the circuit breaker.

It is another object of our invention to provide a low pressure interlock which prevents fluid under pressure from being supplied to the fluid operated means under low I pressure conditions.

Still another object of our invention is to provide a new and improved control valve fora con trol arrangement for fluid operated electric circuit breakers.

Further objects and advantages of our invention will become apparent as the following description proceeds and the features of novelty which characterize our invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of our invention reference may be had to the accompanying drawings in which Fig. l is a schematic diagram, partly in section, of an electric circuit breaker and operating mechanism therefor, employing the control arrangement of our invention, the electrical circuits having been omitted for the sake of simplicity; Fig. 2 is an enlarged sectional view of portions of the mechanical and pneumatic control arrangement of our invention shown in Fig. 1, and Fig. 3 shows the electrical control circuits which have been omitted from Figs. 1 and 2 in order to simplify the disclosures.

ated circuit breaker but it is particularly applicable to fluid operated circuit breakers employing the operating mechanism disclosed and claimed in copending Boisseau et a1. application Serial No. 562,296, filed November 7, 1944, now Patent No. 2,436,190, granted February 17, 1948, and assigned to the same assignee as the present application. Accordingly,'we have disclosed our invention as applied to the operating mechanism of the above mentioned Boisseau et a1. application.

Referring now to the drawings, circuit breaker I is illustrated as comprising a stationary contact 2 and a movable contact 3 arranged to be operated so as to draw an arc in arc chute Contacts 2 and 3 are arranged to be connected with suitable line terminals schematically shown at 5 and 6, respectively. The fixed contact 2 is provided with spring pressed contact fingers 1 and longer arcing contact fingers 8, while movable contact 3 is provided with an arcing tip 9 so that when the contacts separate an arc occurs between fingers I and arcing tip 9. Immediately after the separation of the contacts one terminal of the arc is transferred by a blast of fluid, such as air or other gas, flowing in conduit III from contact fingers 8 to a contact II which is provided with a tip of arc-resistant metal. The fluid blast from conduit I 0 upon opening of the circuit breaker I drives the are into the arc chute 4 against the edges of a plurality of partitions or baffles I2, which partitions are transverse to the arc gap and the'ends of which extend close to the path of movement of the arcing tip 9 of movable contact 3. The circuit breaker is illustrated by way of example only' in order to describe our new and improved control arrangement. The arrangement described thus far is described and claimed in United States Letters Patent 2,284,842,,granted June 21, 1942, and assigned to the same assignee as the present application.

In view of the fact that we have illustrated circuit breaker I as a fluid blastcircuit breaker of the cross air blast type, it is necessary to provide a source of fluid under pressure which is illustrated at I3. Conduit I0 is connected to source I3 through a blastpvalve I 4 having a reciprocally movable valve member I5 connected to a suitable valve stem I6. A spring I I normally biases valve member I 5 to a closed posi tion indicated in Fig. 1.

In order to produce relative movement of contacts 2 and 3 we provide an operating mecha- Our invention is applicable to any fluid opernism In, which is identical with-the operating mechanism disclosed in the above mentioned Boisseau et al. copending application. Operating mechanism is includes a fluid motor comprising a circuit breaker opening piston I9 and a circuit breaker closing piston rigidly interconnected by a rack 2|. Piston i9 is reciprocal in a cylinder 22 while piston is reciprocal in a cylinder 23. Preferably these cylinders 22 and 23 are arranged as one continuous cylinder with a discontinuous part so that a pinion 24 fixedly mounted on a rotatable shaft 25 may engage with rack 2|. With this arrangement the rectilinear motion of the pistons of the fluid motor is translated into rotary motion of shaft 25.

Cylinder 22 is connected to source l3 through conduit 25, circuit breaker opening valve generally indicated at 21, and conduit 25. Similarly, cylinder 23 is connected to source l3 through conduit 29, circuit breaker closing valve generally indicated at 30, and conduit 3|. Circuit breaker opening and closing valves 21 and 30, respectively, are shown in section and considerably enlarged in Fig. 2.

In order to provide accurate speed control of the fluid motor including pistons l3 and 25, we have provided another set of pistons 32 and 33 rigidly interconnected by rack 34, which also engages pinion 24. Pistons 32 and 33 are mounted in cylinders 35 and 35, respectively, which, like cylinders 22 and 23, are preferably arranged as one continuous cylinder, parallel with the continuous cylinder comprising cylinders 22 and 23. It will be obvious that with this arrangement whenever pistons i3 and 20 are moved to the left as viewed in Fig. 1, pistons 32 and 33 will be moved to the right by virtue of pinion 24 whose teeth engage with both racks 2| and 34.

As is brought out in the above mentioned copending Boisseau et al. application, pistons 32 and 33 provide a very desirable means for controlling the speed of operation of the operating mechanism i3 during an operating stroke of the circuit breaker. In order to provide further control cylinder 36 is provided with a spring loaded check valve 31 and a needle valve 35. Similarly, cylinder 35 is provided with a spring loaded check 39 and a needle valve 40. Although pistons l3 and 20 are illustrated as being larger than pistons 32 and 33, it should be understood that these pistons may all be the same size if desired.

From the above description of operating mechanism i8 it is obvious that the fluid motor produces rotation of shaft 25, which may be connected to one or more sets of relatively movable contacts to produce relative movement between said contacts.

Rigidly fastened to shaft 25 and rotatable therewith is a crank arm 4|. Preferably the free end of crank arm 4| is pivotally connected as indicated at 42 with a link 43, the other end oi which is pivotally connected as indicated at 44, to movable contact 3. Preferably link 43 includes a section 45 of insulating material and a gooseneck portion 45 between crank arm 4| and insulation 45. Straight line motion of movable contact 3 is obtained by means of four guide rollers 41 arranged two on either side of movable contact 3.

As is clearly disclosed in the above mentioned Boisseau et a1. copending application, crank arm 4| and link 43 provide a toggle arrangement tending to lock the circuit breaker in both the open and the closed position, shaft 25 rotating slightly more than 180 from the closed to the open position of the circuit breaker.

with the arrangement described above. blast valve N can readily be operated in response to relative movement of contacts 2 and 3 merely by providing a cam 45 on shaft 25 rotatable with shaft 25. Cam 45 is arranged to engage with a roller 59 mounted on a bell crank 55 pivotally mounted at 5|. Bell crank 55 has an extension 52 engageable with blast valve stem l5. Upon rotation of shaft 25 in a counter-clockwise direction, as viewed in Fig. l, blast valve member I5 is mo ed upwardly to the open position to proride a blast of fluid under pressure adjacent relatively movable contacts 2 and 3 before these contacts separate sumciently to draw an arc therebetween.

Rotatable shaft 25 may also control suitable switches and, as illustrated in Fig. l, a switch arm 53 rotatable with shaft 25 normally bridges contacts 54 when the circuit breaker is in the closed posiiton. When the circuit breaker is in the open position switch arm 53 normally bridges two sets of contacts 55 and 55, respectively.

In order to be sure that circuit breaker is not operated unless the pressure in tank or source I3 is sufficiently high, we provide a plurality oi pressure responsive switches 51 and 55. Pressure responsive switch 51 is a minimum opening pressure responsive switch the contacts 59 of which remain closed as long as the pressure in source i3 does not fall below a predetermined value to which the switch has been set and below which value a breaker opening operation might be hazardous or unsafe. Pressure responsive switch 58 is a minimum closing pressure responsive switch and is arranged to bridge or close contacts as long as the pressure remains somewhat above the value for which switch 51 is set. With this arrangement the circuit breaker cannot be closed unless there is sumcient pressure in tank i3 to permit an immediate opening operation if it is required.

In accordance with our invention circuit breaker closing valve 35 is a solenoid-operated closing valve of the differential pressure type somewhat similar to the valves disclosed in United States Letters Patent 1,912,024 and 2,315,991, assigned to the same assignee as the present application. As best shown in Fig. 2, solenoid-operated closing valve 30 is a high speed valve with high flow eiilciency so constructed and arranged as to operate in any position and comprises a valve body 5| in which is reciprocally mounted a valve member 52 arranged to cooperate with an annular valve seat 53. Valve member 52 is connected to a piston 54 reciprocal in a cylinder in valve body 5|. Valve body 5| is provided with suitable passages so that when valve member 52 is in the open position fluid under pressure may flow from conduit 3| to conduit 25. Valve body 5| is also provided with an opening 55 so that when valve member 52 is in the closed position shown in Fig. 1, in engagement with annular valve seat 53, conduit 25 and consequently cylinder 23 of the fluid motor is vented to atmosphere through opening 55. When valve member 52 is moved away from annular seat 53 so as to provide a direct passageway between conduits 3| and 23 a valve member 51 connected to piston operated valve member 52 by a stem 55 closes opening 55 thereby to prevent the escape of gas or air to atmosphere through opening 55. The clearance between piston 54 and the walls of cylinder 55 is such that fluid under pressure may flow past the piston operated valve member into a chamber 55 above piston 54 connected to valve member 82. If desired a suitable passageway such as 18 may be provided to insure that fluid under pressure is admitted to chamber 88.

To obtain maximum opening speed of solenoidoperated closing valve 80, it is desirable to minimize the volume of chamber 68 so that gas or fluid under pressure contained therein may be evacuated in a short interval of time, as will be described hereinafter. Passageway which extends through valve member 62 and piston 84 therefore interconnects chamber 69 with the pressure source l3 through conduit 3| so that as merit, is deenergized. Consequently projection long as fluid is prevented from evacuating from chamber 69, the main valve element functions in known manner as a differential piston to close and maintain the valve 62 properly sealed against the seat 63 by virtue of the difference of effective areas subject to fluid pressure above and below the piston 64. A small spring force may also be provided to bias valve 62 against valve seat 88 so pressure may be built up from zero at source l8 without leaking past what might otherwise be an unseated valve.

In order to cause opening of circuit breaker closingvalve 30 there is provided a pilot valve member 1| which controls the pressure in the chamber 69 and which when opened by being moved in an upward direction from the position shown in Fig. 2, releases the pressure in chamber 69 thereby relieving the pressure acting on piston operated valve member 62 so that the fluid pressure tending to push valve member 82 upwardly is suflicient to move valve member 82 to the open position at high speed. Since fiuid can pass through the relatively large passageway 12 controlled by pilot valve member 1| considerably faster than through the passageway 10 which is relatively small, no material pressure can be built up above piston operated valve member 62 and consequently valve member 62 remains open until either the pilot valve member 1| is closed, or other means is provided to cause closure of valve 82.

In order to operate pilot valve member 1| a concentrically arranged winding 13 is provided relative to valve member 1| whereby pilot valve member 1| acts as an armature and is moved to the open position whenever winding 13 is energized. A suitable spring 14 normally biases pilot valve member 1| to the closed position.

The arrangement described thus far comprises a well known form of pilot operated, differential pressure valve. In prior art arrangementsit was necessary to provide means for accurately timing the energization of solenoid winding 18 to be sure that the valve member 62 remained open for a suflicient length of time completely to close the circuit breaker. In addition to that, a seal-in switch was necessary to supplement the operators control switch so that if the operator released the control switch the closing control valve would not close prematurely. In accordance with our invention the requirement of a precisely timed cut-off switch and a seal-in switch may be dispensed with. The function of the seal-in switch required heretofore is taken care of completely by a finger-like projection on piston 84 extending up toward pilot valve member 1|. When the pilot valve member 1| is opened, as by energization of winding 13, it is moved upwardly and piston'operated valve member 62 is moved to its open position. Finger-like projection 15 therefore follows valve member 1| and maintains it in its open position even though or pin 18, which might be termed a hold-open pin, and which constitutes a mechanical element or means for holding the pilot valve 1| open against the bias of its return spring 14 and which element is controlled by the operation of main valve 82, provides the seal-in means in a very simple manner. It should be understood that although we have shown pin or finger 15 as attached to piston 84, it could equally well be attached to valve member 1|, or not attached to either piston 64 or valve member 1| so long as it was an interference member preventing members 84 and 1| from being closer together than the amount this pin prescribed.

In order to determine the length of time that valve member 62 is in the open position, we have provided a timing chamber 18 which completely encloses solenoid-operated pilot valve.

The fluid under pressure escaping through passageway 12 when pilot valve member 1| is open is retained in timing chamber 16 which has a small escape port 11 to atmosphere. It is obvious that after a period of time the pressure in timing chamber 18, and hence in chamber 88, rises so that the forces tending to close valve member 62 predominate over the forces tending to open valve member 62, whereupon valve member 62 and accordingly pilot valve member 1| close to cut oil the pressure supplied to conduit 29; The pressure accumulated in timing chamber 18 thereupon dissipates through bleed hole 11 at a rate fast enough to prepare for an ensuing operation. By properly proportioning the volume of timing chamber 16 and the cross sectional area of the inlet and outlet bleeds with respect to the operating pressure, satisfactorily consistent cut off timing at the end of the closing stroke of the actuating piston is attainable. The volume of timing chamber 16 may be adjusted by various means such as, for example, the use of fill-disks 18 fastened to one end of timing chamber 16 as by bolt 19.

Circuit breaker opening valve 21 is very similar to circuit breaker closing valve 38 and the corresponding parts thereof are. designated by the same reference numerals in Fig. 2. Pilot valve member 1| acts as an armature with respect to a concentrically arranged winding 80. 'A timing chamber 8| somewhat similar to the timing chamber 16 is provided. The timing chamber 8| functions in exactly the same manner as timing chamber 16 and is provided with an escape port or bleed passageway 82. In fact the only substantial difference between circuit breaker opening valve 21 and circuit breaker closing valve 30 is that in the case of the former it is desirable to provide manual emergency tripping means for the circuit breaker other than through winding 80. To this end an operating rod 88 is provided which is connected to pilot valve member 1| by a lost motion connection indicated at 84. Operating rod 83 extends outside of timing chambe 8| and is mechanically connected to a lever 85 pivotally mounted at 86 to timing chamber 8|. A suitable spring 81 fastened to timing chamber 8| and lever 85 tends to normally move operating rod 83 to the position corresponding to the closed position of pilot valve member 1|. Itwill be obvious that the lost motion connection 84 per mits the winding to control pilot valve member 1| without interference from operating rod 83. A suitable manual means 88 illustrated as a pull chain or wire in Fig. 1 enables the operator to winding 13, which initiated its opening move- I readily trip the circuit breaker by manually open ing pilot valve member 1 I. A suitable stop member preferably limits the maximum upward movement of lever 05.

It has been found desirable to interlock the operating means for the circuit breaker opening and closing control valves in order to prevent failure of the operating mechanism which might be caused by simultaneous energization of windings and 00. Such an interlocking arrangement is disclosed and broadly claimed in United States Letters Patent 2,281,337, Stegelitz et al., granted April 28, 1942, and copending application Serial No. 453,491. Stegelitz et al., filed July 30, 1942 (now abandoned) both assigned to the same assignee as the present application. By virtue of the provision of timing chamber 10 a very simple interlocking arrangement may be obtained. As illustrated in the drawings, conduit connected to the outlet side of circuit breaker opening valve 01 is connected by means of a conduit-90 and a check valve ill with timing chamber 10 of circuit breaker closing valve 00. With this arrangement it is obvious that whenever circuit breaker opening valve 21 is opened fluid under pressure will flow through conduit 90 and check valve 9| to timing chamber 10 and this will either insure that closing valve 00 remains closed or is rapidly moved to the closed position in the event that it is open. Check valve 9i prevents reverse flow of fluid from timing chamber 16 to conduit 90.

It should be observed that the openings 00 in control valves 21 and are relatively large to permit rapid escape to atmosphere of the fluid contained in cylinders 22 and 20.

With the control arrangement described thus far a very simple electrical circuit for controlling the energization of windings 10 and 00 is required. This control circuit is clearly shown in Fig. 3 with the corresponding parts thereof designated by the same reference numerals as in Figs. 1 and 2. The circuit breaker opening winding 00 is energized through the contacts 54 of auxiliary a switch, the contacts 59 of minimum opening pressure responsive switch 51 and the contacts 00 of a manually operable trip switch 90. The Eircuit Just described is connected across a source of control power 94. If desired, a suitable indicating means, such as a light 95, may also be controlled by the contacts 54 of the a switch thereby indicating when the circuit breaker is in the closed position.

In order to close the circuit breaker a manually operable close switch 90 is provided for bridging contacts 91 connected in series with contacts 00 of minimum closing pressure responsive switch 50, in series with contacts of the b auxiliary switch, in series contacts 90 of a relay 99 having a winding I00, and in series with winding 10 of circuit breaker closing valve 00. This series circuit is connected across control power source 94. When the circuit breaker is in the open position and the pressure in source I0 is suiilciently high, contacts 50 and 56 will be closed and closing of close switch 96 will energize winding 10 to initiate the closing operation of the circuit breaker. Relay 99 is provided with a short time delay pick-up and its winding I00 is connected across power source 94 through contacts 60 and close switch 00. This relay 99 prevents pumping of the circuit breaker operating mechanism in the event that the operator fails to release the close switch 90. The opened condition of the circuit breaker may be indicated by a suitable signal light IOI connected across the power source 94 through the contacts of an auxiliary b switch 00. An examination oi the control circuit of Fig. 3 clearly indicates the simplicity thereof which requires no seal-in arrangement for close and trip switches 00 and 00 and no timing relays or cut oi! switches for timing the opening period of circuit breaker control valves 21 and 00.

As explained earlier, the minimum pressure responsive switches 01 and 00 will open their contacts to prevent operation of circuit breaker I if the pressure conditions fall below the predetermined values to which they have been set and below which values the source pressure might be insuiiicient for safe operation. It is also desirable to prevent operation of the manual emergency pull wire 00 if the pressure conditions in source I0 are too low for safe operation. Accordingly, we provide a minimum pressure lockout device generally indicated at I02 in Figs. 1 and 2, which includes a lock-out prop I00 engageable with an extension I04 of lever 00. Low pressure lock-out device I02 should be responsive to the pressure in source or tank I0 and accordingly is provided with an air cylinder I05 which is connected to source I0 by a conduit I00. Within air cylinder I05 is a Sylphon bellows I01. Air pressure admitted to cylinder I05 is applied to the exterior of the bellows and this force is transmitted to a thrust pin I00, the end of which may engage with lock-out prop I00. A suitable spring I09 is slipped over thrust pin I00 and compressed between a piston member IIO, slidable in cylinder I05 and forming one end of bellows I01, and an adjustable nut III on thrust pin I00. By adjusting nut III the loading of Sylphon bellows I01 may be controlled. Spring I09 is designed with the same gradient as the mechanical gradient of Sylphon bellows I01 and serves as a balance to keep the thrust pin I00 against lock-out prop I 03 both during assembly and also between the range of no air pressure and the low pressure limit at which the apparatus is set to work. Thus no movement is caused of the Sylphon bellows as the pressure builds up from zero pounds per square inch to the lower limit of the range of operation. This feature greatly increases the life of the apparatus and actually the Sylphon bellows I01 is deflected only between the differential pressure limits and not through the pressure range of the device.

Cylinder I05 is preferably bolted to the side of a case III which has an opening II3 through which lock-out prop I00 may extend. The edges of opening 0 act as stops to determine the maximum movement of lock-out prop I00 and consequently prevent further deflection of the Sylphon bellows I01 at pressures above the upper diflerential pressure limit.

Lock-out prop I00 is pivotally mounted as indicated at II4 to a rocker arm II5 pivotally mounted at IIB to a support II1 mounted in case III. Rocker arm H5 is biased by means of a spring H0 against a stop block IIO. When the prop I00 operates as an interference member to prevent lever from being rotated around pivot 00 a thrust is applied endwise so that the spring H0 is compressed and the rocker arm slightly rotates so that the load is transferred directly to the thrust block I20. It will be understood that instead of mounting lock-out prop I00 on rocker arm II5 it could be mounted on a resilient bearing of spring wire so that when the bearing deflects the load is transferred to the thrust block I20.

In order to control the range of operation for the look-out device there is provided a thrust pin I2I engaging lock-out prop I03 in opposed relationship to thrust pin I00. A suitable loading spring I22 is provided and the thrust may be adlusted by adjustable screw I23. In an arrangement which we built and tested, by proper adjustment of loading screw I23 and retainer nut III, the effective zone of operation could be varied between 91 pounds and 230 pounds per square inch.

In order that lock-out prop I03 operates with a snap action and is always in either one of its extreme positions, a pair of adjustable magnets I24 and I25 are provided arranged one on either side of lock-out prop I03. By properly adjusting the air gap between magnets I24 and I25 the pressure diflerential for operating lock-out prop I03 may be varied over a range from two to twenty pounds per square inch.

As indicated in the drawings, the circuit breaker is in the closed position with the pressure in tank I3 at its normal value. Ii the pressure should drop below the predetermined minimum value at which the device I02 has been set, this value being that below which operation of the breaker might be rendered unsafe, lock-out prop I03 would snap over under the extension I04 of lever 85 to prevent manual operation of pilot valve member II of circuit breaker opening valve 21. Furthermore, minimum pressure responsive relays 51 and 58 would also open their associated contacts so that operation of the circuit breaker could not be obtained, neither manually, nor electrically, without flrst restoring an adequate working pressure in source I3.

In view of the detailed description included above, the operation of the control arrangement of our invention will be obvious to those skilled in the art. When the pressure in source I3 is sufllciently high, opening of the circuit breaker may be initiated either by operating manual pull wire 88 or depressing trip switch 93, whereupon, pilot valve member II of circuit breaker opening valve 21 is opened with the consequent opening of the associated valve member 62. pressure is admitted to cylinder 22 and also to timing chamber 19 through duct 90 so that circuit breaker closing valve 30 is rapidly moved to the closed position if open or maintained in the closed position it closed. Hold-open pin I5 0 insures that valve 21 remains open until timing chamber III has functioned to close valve 21.

A circuit breaker closing operation may be initiated when the circuit breaker is in the open position by depressing close switch 96 which functions to cause opening of circuit breaker closing valve 30 to supply fluid under pressure to cylinder 23. Timing chamber I6 times the period that fluid is supplied to cylinder 23 and insures a complete opening operation. If desired, suitable contacts I26 may be provided in parallel with the contacts 92 associated with trip switch 93. Contacts I26 may be controlled in response to a suitable overload relay or the like toautomatically initiate opening of the circuit breaker in response to predetermined abnormal conditions on the line, the terminals of which are designated as 5 and 6.

While we have shown and described a particular embodiment of our invention, it will be Fluid under time as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent oi the United States is:

1. In a control system for'a fluid operated circuit breaker, a valve comprising a fluid operated main valve member, a pilot valve the opening of which initiates operation of said main valve member, means for opening said pilot valve, and means for holding said pilot valve in the open position once it and said main valve have both opened comprising an extension movable with said main valve member for engaging said pilot valve.

2. In a control system for a fluid operated circuit breaker, a valve of the differential pressure type comprising a fluid operated main valve member, a pilot valve member the opening of which affects the pressures acting on said main valve member to cause openin of said main valve member, means for opening said pilot valve, and mechanical means operable in response to opening movement of said main valve member for holding said pilot valve in the open position.

3. In a control system for a fluid operated circuit breaker, a valve comprising a fluid operated main valve member, a pilot valve the opening of which initiates operation of said main valve member, means for opening said pilot valve, means for holding said pilot valve in the open position once it has opened comprising an extension movable with said main valve member, and means for timing the open condition of said main valve member comprising a chamber enclosing said pilot valve and receiving the fluid discharged through said pilot valve.

4. Ina control system for a fluid opera-*- 1 circuit breaker, a valve of the differential pressure type comprising a fluid operated main valve member, a pilot valve the opening of which ailects the pressures acting on said main valve member to cause opening of said main valve member, means for opening said pilot valve, means for holding said pilot valve in the open position once it has opened comprising an element controlled by the operation of said main valve member, and means for timing the open condition of said main valve member comprising a chamber enclosing said pilot valve and receiving the fluid discharged through said pilot valve.

5. In a control system for a fluid operated electric circuit breaker, a double-acting fluid motor, a source of fluid under pressure, a first valve for connecting said source to one side of said fluid motor, a second valve for connecting said source to the other side of said fluid motor, each of said valves being of the differential pressure type including a fluid operated .main valve member, a

pilot valve the opening of which affects the pressures acting on said main valve member for opening said main valve member, and means for holding said pilot valve in the open position once it has opened comprising a flnger-like extension on said main valve member extending toward said pilot valve member.

'6. In a control system for a fluid operated electric circuit breaker, a double-acting fluid motor, a source of fluid under pressure, a flrst valve for connecting said source to one side of said fluid motor, a second valve for'connecting said source to the other side of said fluid motor, each of said valves being of the differential pressure type and comprising a fluid operated main valve member, a pilot valve the opening of which aflects the pressur s acting on said main valve member to 11 cause an opening operation thereof, and mechanical means for holding said pilot valve in the open position once it has opened, said mechanical means being controlled by the operation of said main valve member.

7. In a control system for a fluid operated electric circuit breaker, a double-acting fluid motor, a source of fluid under pressure, a flrst valve for connecting said source to one side of said fluid motor, a second valve for connecting said source to the other side of said fluid motor, each of said valves being of the differential pressure type and comprising a fluid operated main valve member, a pilot valve the opening of which affects the pressures acting on said main valve member to cause the opening thereof; means for timing the open condition of said main valve member of said first valve comprising a first timing chamber associated therewith, means for timing the open condition of said main valve member of said second valve comprising a second timing chamber associated therewith, and means for interlocking said flrst and second valves comprising a conduit interconnecting the outlet of one of said valves with the timin chamber of the other valve.

8. In a control system for a fluid operated electric circuit breaker, a double-acting fluid motor, a source of fluid under pressure, a flrst valve for connecting said source to one side of s id fluid motor, and a second valve for conn cting said source to the other side of said fluid motor. each of said valves bein of the differential pressure type including a fluid operated main valve member, a pilot valve the opening of which affects the pressures acting on said main valve member to cause the openin thereof. and means for timing the open condition of said main valve member comprising a timing chamber associated therewith.

9. In a control svstem for a fluid operated electric circuit b eaker, a double-acting fluid motor, a source of fluid under pressure, a flrst valve for connecting said source to one S'de of said fluid motor, a second valve for connecting said source to the other side of said fluid motor, each of said valves being of the differential pressure type including a fluid operated main valve member, a pivot valve the opening of which affects the pressures acting on said main valve member to cause the opening thereof, and means for timing the open condition of said main valve member comprising a timing chamber associated therewith; and means for interlocking said first and second valves comprising a conduit interconnecting the outlet of said first valve with the timing chamber of said second valve whereby said second valve is closed whenever said flrst valve is opened.

10. In a control system for a fluid operated electric circuit breaker, a double-acting fluid motor, a source of fluid under pressure, a flrst valve for connecting said source to one side of said fluid motor, a second valve for connecting said source to the other side of said fluid motor, each of said valves being of the differential pressure type including a fluid operated main valve member, a pilot valve the opening of which affects the pressures acting on said main valve member to cause the opening thereof, and means for timing the open condition of said main valve member comprising a timing chamber associated therewith; means for interlocking said flrst and second valves comprising a conduit interconnecting the outlet of said first valve with the timing chamber of said second valve whereby said sec- 12 ond valve is closed whenever said first valve is opened, and means for preventing the flow of fluid from said timing chamber of said second valve to said conduit.

11, In a control system for a fluid operated circuit breaker, a source of fluid under pressure, a valve for controlling the flow of fluid from said source comprising a fluid operated main valve member, a pilot valve the opening of which initiates operation of said main valve member, means for holding said pilot valve in the open position once it has opened comprising an element controlled by the operation of said main valve member, manually operable means for opening said pilot valve, and means including an interference member responsive to the pressure of the fluid of said source for mechanically blocking opening movement of said manually operable means when the pressure of said source falls below a predetermined minimum value.

12. In a control system for a fluid operated circuit breaker, a source of fluid under pressure, a valve for controlling the flow of fluid from said source comprising a fluid operated main valve member, a pilot valve the opening of which initiates operation of said main valve member, manually operable means including an interference member for opening said pilot valve, and means responsive to the pressure of the fluid of said source for mechanicall blocking opening movement of said manually operable means when the pressure of said source falls below a predetermined minimum value.

13. In a control system for a fluid operated circuit breaker, a source of fluid under pressure, a valve for controlling the flow of fluid from said source comprising a fluid operated main valve member, a pilot valve member the opening of which initiates operation of said main valve member, means for holding said pilot valve member in the open position once it has opened com prising an element movable in accordance with the operation of one of said valve members, manually operable means for opening said pilot valve, and means including an interference member responsive to the pressure of the fluid of said source for mechanically blocking opening movement of said manually operable means when the pressure of said source falls below a predetermined minimum value.

14. In a control system for a fluid operated circuit breaker, a valve comprising a fluid operated main valve member, a pilot valve member the opening of which initiates the operation of said main valve member, means for opening said pilot valve member, and means for holding said pilot valve member in the open position once it has opened comprising an element mounted on and movable with one of said valve members, the holding ability of said element being dependent upon the operation of said main valve member.

15. In a control system for a fluid operated electric circuit breaker, a double-acting fluid motor, a source of fluid under pressure, a first valve for connecting said source to one side of said fluid motor, a second valve for connecting said source to the other side of said fluid motor, each of said valves being of the differential pressure type and comprising a fluid operated main valve member, a pilot valve member the opening of which afl'ects the pressures acting on said main valve member to cause an opening operation thereof, and means for holding said pilot valve member in the open position once it has opened comprising an element disposed between 13 said two valve members for preserving a minimum spacing between said valve members.

16. In a control system for a fiuid operated circuit breaker, a source of fluid under pressure, a valve for controlling the flow of fluid from said source comprising a fluid operated main valve manner, a pilot valve the opening of which initiates operation of said main valve member, means for opening said pilot valve, means for preventing the operation of said means for opening said pilot valve comprising a movable interference member, and means for moving said interference member with snap action into interfering position in response to the pressure of 14 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 410,183 Ongley Sept. 3, 1889 560,230 Powers May 19, 1896 653,187 Smith July 3, 1900 932,244 Bowman Aug. 24, 1909 1,990,741 Marvel Feb. 12, 1935 2,207,806 Hollmann July 16, 1940 2,281,337 Stegelitz Apr. 28, 1942 2,372,729 Molloy Apr. 3, 1945 Certificate of Correction Patent N 0. 2,500,777

JULIUS W. TIMMERMAN, JR., ET AL.

It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 1%, line 48, for the Word pivot read pilot; column 13, line 7, for manner read mem er;

and that the said Letters Patent should be read With these corrections therein that the same may conform to the record of the case in the Patent Oflice. Signed and sealed this 26th day of September, A. D. 1950.

March 14, 1950 THOMAS F. MURPHY,

Assistant Oomz'sez'oner of Patents,

Certificate of Correction Patent No. 2,500,777 March 14, 1950 JULIUS W. TIMMERMAN, JR., ET AL.

It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 11, line 48 for the word pivot read pilot; column 13, line 7, for man- ,I d b ner rea mem er;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Ofiice. Signed and sealed this 26th day of September, A. D. 1950.

THOMAS F. MURPHY,

Assistant Oomnissz'oner of Patents. 

